diff --git a/libs/langchain-google-common/src/chat_models.ts b/libs/langchain-google-common/src/chat_models.ts
index 1de5280fbe72..7d476b94cf2c 100644
--- a/libs/langchain-google-common/src/chat_models.ts
+++ b/libs/langchain-google-common/src/chat_models.ts
@@ -469,6 +469,7 @@ export abstract class ChatGoogleBase<AuthOptions>
     }
     const llm = this.bind({
       tools,
+      tool_choice: functionName,
     });
 
     if (!includeRaw) {
diff --git a/libs/langchain-google-common/src/utils/gemini.ts b/libs/langchain-google-common/src/utils/gemini.ts
index 48bd41fb5c2f..23c46f3783db 100644
--- a/libs/langchain-google-common/src/utils/gemini.ts
+++ b/libs/langchain-google-common/src/utils/gemini.ts
@@ -1047,10 +1047,20 @@ export function getGeminiAPI(config?: GeminiAPIConfig): GoogleAIAPI {
       return undefined;
     }
 
+    if (["auto", "any", "none"].includes(parameters.tool_choice)) {
+      return {
+        functionCallingConfig: {
+          mode: parameters.tool_choice as "auto" | "any" | "none",
+          allowedFunctionNames: parameters.allowed_function_names,
+        },
+      };
+    }
+
+    // force tool choice to be a single function name in case of structured output
     return {
       functionCallingConfig: {
-        mode: parameters.tool_choice as "auto" | "any" | "none",
-        allowedFunctionNames: parameters.allowed_function_names,
+        mode: "any",
+        allowedFunctionNames: [parameters.tool_choice],
       },
     };
   }